Iran today made its strongest statement yet that it believes a Western plot is behind the Stuxnet worm that has infected tens of thousands of computers in the country, including some at its sole nuclear power plant.

"It is hard for the Western states to tolerate the progress of Iran's peaceful nuclear program," said Mehmanparast in a summary of the briefing posted to the Ministry of Foreign Affairs Web site.

"Western states are trying to stop Iran's (nuclear) activities by embarking on psychological warfare and aggrandizing, but Iran would by no means give up its rights by such measures," Mehmanparast said, reacting to reports that Stuxnet had caused delays at the Bushehr nuclear reactor.

In the last two weeks, Iranian officials have acknowledged that Stuxnet infected at least 30,000 Windows PCs in the country, among them some used by workers at the Bushehr nuclear power plant. Iran has repeatedly denied that the worm had infiltrated the industrial control systems at Bushehr, damaged the facility or caused any delay in its completion.

On Monday, Ali Akbar Salehi, who heads Iran's Atomic Energy Organization, said that although Bushehr would not reach full generating capacity until 2011, it would hit the 40% mark in December, according to the semi-official Fars News Agency.

A leak in a containment pool, which has since been fixed, was the cause of the most recent delay, Salehi claimed.

Western countries, including the U.S., suspect that other aspects of Iran's nuclear program are cover for enriching uranium into weapons-grade fuel. The Bushehr plant is not considered a proliferation risk by the U.S. Department of State, however, in large part because the reactor is Russian-operated.

Iran has steadily stepped up its campaign to pin blame for Stuxnet on a deliberate plot aimed at the country's nuclear plans. Last weekend, Heydar Moslehi, the government's minister of intelligence, said that "enemy spy services" were responsible for Stuxnet.

It's unlikely that the makers of Stuxnet were based in Iran; malware authors do not have to be in physical proximity to their targets.

Security experts have said that Stuxnet's complex design and its intent to hijack SCADA industrial control systems indicates that it was almost certainly the work of a state-backed group of programmers, while the large number of infections in Iran hinted that it was the most likely target.

None of those suspicions have been confirmed by researchers who have poured over Stuxnet's code, although some have spotted clues that either point to Israel or to an attempt by the hackers to pin blame on the country.

Stuxnet, which was first launched in June 2009 but didn't pop into public view until a year later, has been described as "groundbreaking" for its ability to infiltrate networks, sniff out SCADA systems and reprogram the hardware controllers that monitor and manage machinery in factories, power plants, pipelines and military installations.